To help celebrate the release of Aniston's "Horrible Bosses," Cox turned up to hang with her BFF and her new beau Thursday night at the flick's official premiere after party.

Partying at Hollywood's Colony nightclub, Cox, 47, joined Aniston, 42, and Theroux, 39, to nosh on chow mein and other snacks at the exclusive bash, attended by Jason Bateman, Jennifer Love Hewitt and others.

"Jen had a glow to her and looked amazing; it was obvious she was in a good state of mind," a source at the bash told Us Weekly of Aniston, who took her romance with the actor-screenwriter public earlier this month.

In the weeks since debuting her new relationship, Aniston has adopted a relaxed approach when it comes to packing on the PDA with her beau.

"She doesn't want him to get frustrated with her usual covert way of doing things," a Theroux source told Us of Aniston's decision to come out of hiding with their romance. "So she's compromising and relaxing about the paparazzi."

Her plan of action appears to be working quite well thus far. "Yes, I'm very happy," the actress recently said during a "Good Morning America" press appearance when asked about her personal life. "I'm extremely lucky, and I'm extremely happy."